That's right, there is nothing you CAN do for him beyond taking him immediately to a vet. It's not just the swelling that's the issue. Though it sounds as if it could be caused by a hemorrage. It's the things you can't see, -what might be damaged inside him, and he could have serious internal injuries.
I hope he's ok. Post back if you get the chance, to tell us how he's doing.
You have to do the same thing for your dog that you would do if this were your child. You MUST take him to a vet. This is an emergency so please go to the nearest ER vet now. He may very well have severe internal injuries that need to be evaluated. Most facilities will work with you on financing. If you end up not being able to afford treatment, then you must do right by him and put him down or surrender him to a shelter or someone else who can afford it. What you can't do is nothing and let him suffer and die without care.